Temporal relationship between decrease in antimicrobial prescription for Danish pigs and the "Yellow Card" legal intervention directed at reduction of antimicrobial use.

The potential effects of the "Yellow Card" intervention, enforced by Danish authorities in December 2010, on the antimicrobial prescription in the Danish pig production were investigated. Data on antimicrobial prescription for pigs during 2002-2012 was obtained from the national database on veterinary prescribed medicines, VetStat. Descriptive analysis of temporal trends in quantitative antimicrobial prescription for pigs on national level was performed for each administration route, age group and disease group. In addition, prescription patterns of the three most prescribed antimicrobial classes (tetracyclines, macrolides and pleuromutilins) for weaners and finishers were studied at herd level. A 25% decline in the total antimicrobial use per pig produced occurred between 2009 and 2011. A decline was observed both in sows and piglets (31%), weaners (34%) and finishers (19%). Reduced prescription of tetracycline, macrolides and pleuromutilins for oral use, mainly for gastrointestinal disease (GI) in weaners and finishers, explained 76% of the total reduction. In 2012, the overall antimicrobial use increased by 10%, as a partial reversal of the preceding changes in prescription pattern. On herd level, the decline and subsequent increase was mainly related to changes in number of herds receiving regular monthly prescriptions. This study demonstrated that the steep decrease in antimicrobial use in the Danish pig production was temporally related with the announcement and introduction of the Yellow Card intervention.